1. Technical Field
The present disclosure relates generally to medical devices. More specifically, the present disclosure relates generally to systems and methods for controlled tissue compression.
2. Background of the Related Art
Some surgical procedures require the compression, e.g., clamping, of a patient's tissue. Such procedures may include, e.g., anastomosing, stapling, and resecting of tissue. For example, where cancerous tissue is identified in a patient's gastrointestinal tract, the cancerous tissue may need to be surgically removed. Where, for example, the cancerous tissue is located on the colon and is accessible by surgical instrumentation, the surgeon may make an incision in the patient's abdomen to allow access to the bowel. The surgeon may then use a linear cutting and stapling device, such as that described in U.S. patent application Ser. No. 12/235,362, filed on Sep. 22, 2008, which is expressly incorporated herein in its entirety by reference, to cut and staple the colon tissue on opposite sides of the cancerous portion to be removed. In this procedure, the colon is externally clamped (e.g., between opposed jaws) to compress the tissue. While the tissue is compressed, a cutter and a stapler are activated to make a linear cut and apply typically two linear rows of staples in the areas adjacent the cut. The stapling thus closes both open ends of the portion of the bowel to be removed, as well as providing a temporary closure of the two cut ends of the bowel. This closure limits exposure of the surrounding tissue to the interior of the bowel, thus limiting the risk of infection. After the cutting and stapling procedure, the cancerous portion of tissue may be removed from the patient's body.
After the resection of the cancerous tissue, the surgeon may employ an anastomosing and stapling device, e.g., a circular stapler/cutter. During this procedure, a head portion is positioned within the colon adjacent one of the cut ends and a base or shaft portion is positioned within the colon adjacent the other cut end. The head portion and the base portion may be coupled via a shaft and/or cable that extends out of one cut end and into the other. Via this coupling, the surgeon is able to actuate the anastomosing and stapling device to draw the head portion and the base portion together. After the two cut ends of the colon contact each other, the actuation continues such that the two portions of the colon are clamped together at an annular area of contact. While clamped, the anastomosing and stapling device may be further actuated to apply an annular ring of staples into the compressed tissue. The device may also cut excess tissue disposed within the colon. The head portion and the base portion are then moved apart and the anastomosing and stapling device removed from the patient.
To achieve effective stapling in the above procedures, the tissue must be compressed to the extent that there is an adequately small tissue gap, e.g., one millimeter, between the faces of the tool. If the clamping structures of the instrument are exposed to enough force, maintaining a uniform target tissue gap across the length of tissue to be stapled may be difficult or even impossible. For example, where the clamping structures are cantilevered jaws of a linear stapler, the distal portion of the jaws may splay outwardly from each other under high clamping forces. Where one or both of the jaws splay in this manner, the tissue gap typically increases toward the distal ends of the jaws. Where this tissue gap exceeds an acceptable range, staples may not adequately close the tissue to prevent contamination. This may result from, e.g., the initial stapled gap being too large and/or failure of the staple (e.g., separation from one or more of the portions of stapled tissue) due to improper formation resulting from, e.g., too large a gap between a staple pusher and an anvil that closes the staple.
Powered stapling devices may use control systems and algorithms to control a driving motor in order to properly clamp tissue and achieve a desired tissue gap. Many of these algorithms use standard variables that are based on type of tissue being clamped, type of disease affecting the tissue, the stage of the disease, etc along with typical characteristics of the stapling device itself. However, because each stapling device is different due to motor variation, device construction, wear, mechanical tolerances and mechanical play etc., the variables used in one stapling device to achieve a desired tissue gap may not be effective in a different stapling device of the same type. There is a need to calibrate powered stapling devices and provide inputs to the device control systems in order to improve optimum tissue gaps and staple formation while stapling